.TH MPI_Compare_and_swap 3 "6/7/2023" " " "MPI"
.SH NAME
MPI_Compare_and_swap \-  Perform one-sided atomic compare-and-swap. 
.SH SYNOPSIS
.nf
.fi
.nf
int MPI_Compare_and_swap(const void *origin_addr, const void *compare_addr,
void *result_addr, MPI_Datatype datatype,
int target_rank, MPI_Aint target_disp, MPI_Win win)
.fi


.SH INPUT PARAMETERS
.PD 0
.TP
.B origin_addr 
- initial address of buffer (choice)
.PD 1
.PD 0
.TP
.B compare_addr 
- initial address of compare buffer (choice)
.PD 1
.PD 0
.TP
.B datatype 
- datatype of the element in all buffers (handle)
.PD 1
.PD 0
.TP
.B target_rank 
- rank of target (non-negative integer)
.PD 1
.PD 0
.TP
.B target_disp 
- displacement from start of window to beginning of target buffer (non-negative integer)
.PD 1
.PD 0
.TP
.B win 
- window object (handle)
.PD 1

.SH OUTPUT PARAMETERS
.PD 0
.TP
.B result_addr 
- initial address of result buffer (choice)
.PD 1

.SH NOTES
This operation is atomic with respect to other "accumulate" operations.

The parameter datatype must belong to one of the following categories of
predefined datatypes: C integer, Fortran integer, Logical, Multi-language
types, or Byte as specified in Section 5.9.2 on page 176. The origin and result
buffers (origin_addr and result_addr) must be disjoint.

.SH NOTES FOR FORTRAN
All MPI routines in Fortran (except for 
.I MPI_WTIME
and 
.I MPI_WTICK
) have
an additional argument 
.I ierr
at the end of the argument list.  
.I ierr
is an integer and has the same meaning as the return value of the routine
in C.  In Fortran, MPI routines are subroutines, and are invoked with the
.I call
statement.

All MPI objects (e.g., 
.I MPI_Datatype
, 
.I MPI_Comm
) are of type 
.I INTEGER
in Fortran.

.SH ERRORS

All MPI routines (except 
.I MPI_Wtime
and 
.I MPI_Wtick
) return an error value;
C routines as the value of the function and Fortran routines in the last
argument.  Before the value is returned, the current MPI error handler is
called.  By default, this error handler aborts the MPI job.  The error handler
may be changed with 
.I MPI_Comm_set_errhandler
(for communicators),
.I MPI_File_set_errhandler
(for files), and 
.I MPI_Win_set_errhandler
(for
RMA windows).  The MPI-1 routine 
.I MPI_Errhandler_set
may be used but
its use is deprecated.  The predefined error handler
.I MPI_ERRORS_RETURN
may be used to cause error values to be returned.
Note that MPI does 
.B not
guarantee that an MPI program can continue past
an error; however, MPI implementations will attempt to continue whenever
possible.

.PD 0
.TP
.B MPI_SUCCESS 
- No error; MPI routine completed successfully.
.PD 1
.PD 0
.TP
.B MPI_ERR_ARG 
- Invalid argument.  Some argument is invalid and is not
identified by a specific error class (e.g., 
.I MPI_ERR_RANK
).
.PD 1
.PD 0
.TP
.B MPI_ERR_DISP 
- 
.PD 1
.PD 0
.TP
.B MPI_ERR_RANK 
- Invalid source or destination rank.  Ranks must be between
zero and the size of the communicator minus one; ranks in a receive
(
.I MPI_Recv
, 
.I MPI_Irecv
, 
.I MPI_Sendrecv
, etc.) may also be 
.I MPI_ANY_SOURCE
\&.

.PD 1
.PD 0
.TP
.B MPI_ERR_WIN 
- Invalid MPI window object
.PD 1
.PD 0
.TP
.B MPI_ERR_OTHER 
- Other error; use 
.I MPI_Error_string
to get more information
about this error code. 
.PD 1

